Apache Hadoop 3.1.3 Release Notes

These release notes cover new developer and user-facing incompatibilities, important issues, features, and major improvements.

NameNodes rely on independent block token key ranges to communicate block token identities to DataNodes and clients in a way that does not create conflicts between the tokens issued by multiple NameNodes. HDFS-6440 introduced the potential for overlaps in key ranges; this fixes the issue by creating 64 possible key ranges that NameNodes assign themselves to, allowing for up to 64 NameNodes to run safely. This limitation only applies within a single Namespace; there may be more than 64 NameNodes total spread among multiple federated Namespaces.

The above patch will resolve the race condition

During a rolling upgrade from Hadoop 2.x to 3.x, NameNode cannot persist erasure coding information, and therefore a user cannot start using erasure coding feature until finalize is done.